Memory devices are typically provided as internal, semiconductor, integrated circuits in computers or other electronic devices. There are many different types of memory including random-access memory (RAM), read only memory (ROM), dynamic random access memory (DRAM), synchronous dynamic random access memory (SDRAM), and flash memory. Flash memory devices have developed into a popular source of non-volatile memory for a wide range of electronic applications. Flash memory devices typically use a one-transistor memory cell that allows for high memory densities, high reliability, and low power consumption. Common uses for flash memory include personal computers, personal digital assistants (PDAs), digital cameras, and cellular telephones. Program code and system data such as a basic input/output system (BIOS) are typically stored in flash memory devices for use in personal computer systems.
An increase in the performance and density of flash memory transistors is needed as the performance of computer systems increases. To accomplish the density and performance increase, the transistors have been reduced in size, resulting in increased speed with decreased power requirements. However, further reductions in size are often limited by the lower limit of dimensions that can be achieved using lithographic methods. For example, structures such as conductive lines having features (e.g., line width) of 57.5 nanometers (urn) or less are difficult to produce by standard lithographic methods, and are referred to herein as “sub-lithographic” features.
Attempts have been made to prepare sub-lithographic features by other methods known in the art. For example, electron beam (e-beam) lithography and extreme ultraviolet (EUY) lithography have been used in attempts to prepare such sub-lithographic features. Although such methods can be capable of preparing sub-lithographic features, widespread use of such methods has been hampered by difficulties including, for example, high costs and/or incompatibility with high throughput production methods.
For the reasons stated above, and for other reasons stated below which will become apparent to those skilled in the art upon reading and understanding the present specification, there is a need in the art for methods for preparing sub-lithographic features.